docs: def _validate_raw_nc(self):
          """Checks that raw netCDF file has the right dimensions and variables.
  
          Returns
          -------
          int:
              Length of rivid dimension.
          int:
              Length of time dimension.
  
          Remarks: Raises exception if file doesn't validate.
          """
          self.raw_nc_list = []
          # add one for the first flow value RAPID
          # does not include
          total_time_len = 1
          id_len_list = []
          for rapid_output_file in self.rapid_output_file_list:
              qout_nc = RAPIDDataset(rapid_output_file)
              id_len_list.append(qout_nc.size_river_id)
              total_time_len += qout_nc.size_time
              self.raw_nc_list.append(qout_nc)
  
          # make sure river id lists are the same
          for id_len_undex in range(1, len(id_len_list)):
              if id_len_list[id_len_undex] != id_len_list[0]:
                  raise Exception("River ID size is different in "
                                  "one of the files ...")
  
          for raw_nc_index in range(1, len(self.raw_nc_list)):
              if not (self.raw_nc_list[raw_nc_index].get_river_id_array() ==
                      self.raw_nc_list[0].get_river_id_array()).all():
                  raise Exception("River IDs are different in "
                                  "files ...")
  
          return id_len_list[0], total_time_len